Generic ground compaction rollers are employed to increase the stability of an underlying ground and thus the load bearing capacity of said ground, for example for roads or buildings, i.e., to compact the underlying ground to a desired stability. For this, the generic ground compaction rollers, which are preferably self-propelled, frequently include a machine frame, a drive unit and at least one roller drum mounted on the machine frame for rotation about a rotation axis. In the case of a tandem roller, the ground compaction roller typically includes two roller drums, which are, for example, each connected to the machine frame via a pivot joint or are mounted on two machine frame halves connected to each other via an articulated joint. The machine weight of the tandem roller is distributed over the two roller drums and utilized for compaction of the ground. The traveling mechanism of a single-drum roller, on the other hand, typically includes only one roller drum which is complemented by a pair of wheels. In working operation of the ground compaction roller, the latter typically travels in a working direction across the underlying ground to be compacted. In operation, the ground compaction rollers oftentimes alternate between forward and backward travels. To influence, and in particular increase, the compaction of the ground using the generic ground compaction rollers, the ground compaction rollers usually include an exciter device arranged at least partially in the roller drum. This exciter device is also called an oscillation or vibration exciter. It typically comprises an imbalance mass which is set into rotation by an exciter motor and thereby caused to apply oscillations or vibrations to the roller drum. A corresponding ground compaction roller is known, for example, from DE 10 2014 018 457 A1.
In working operation of the generic ground compaction rollers, the underlying ground is typically passed several times until a desired compaction has been achieved. To recognize the point at which there is no use in performing further passages with the ground compaction roller because the ground is already compacted sufficiently or has almost reached its maximum compaction, it is known to provide the ground compaction rollers with a sensor device for measuring a parameter related to the current ground compaction. For this, the sensor device comprises one or more accelerometers with which the so-called ground stiffness of the ground material to be compacted can be ascertained as a measure for the degree to which the ground has already been compacted. A method for calculating the ground stiffness is known, for example, from EP 2 627 826 B1.
The prior art sensor devices are typically arranged on the machine frame, for example on a drum bearing, of the ground compaction roller. A disadvantage of such an arrangement is that the roller drums are usually vibration-decoupled, or vibration-damped, relative to the machine frame, and in particular the drum bearings on the machine frame, for example through suitable rubber dampers etc. In addition to a desired vibration decoupling between the roller drum and the machine frame, the oscillation of the roller drum is further damped by the play of the travel bearing via which the roller drum is connected to the machine frame. The oscillations of the roller drum, from which the ground stiffness can be calculated, are thus not fully transferred to the machine frame and thus the sensor device. This effect increases with the age of the ground compaction roller due to wear of the travel bearing and the resulting increase in play. As a result, the determination of the ground stiffness through the sensor device is relatively inaccurate in the prior art ground compaction rollers. To avoid these problems, DE 10 2011 088 567 A1 already suggests an even distribution of multiple sensors along the inner circumference of the drum shell to obtain a more accurate picture of the actual movement of the roller drum. However, the implementation of such a system is complicated due to the plurality of necessary sensors and the necessity to process the signals in a central evaluation unit.